It would appear there was a bonfire night party at a Rugby club next to the M5, right where the accident happened. Eyewitnesses at the time said there was a lot of smoke on the motorway, and the Police are now looking into this as the potential cause of the accident. Drivers complained of a "fog wall" that completely impaired vision, and that there was a lot of braking going on at this part of the motorway.
It only takes one wrong move by one driver to cause chaos on the motorway.
God bless all those affected.